1. Field of the Invention
The present invention relates to an I/O control system including a numerical controller that controls a machine such as machine tool, robot, pressing machine, injection molding machine, electric discharge machine, and laser beam machine by which work pieces are machined and amplifiers, motors, and an I/O control unit that are connected to the numerical controller through communication lines.
2. Description of the Related Art
In such a machine as machine tool, a numerical controller is usually connected to motor driving parts and to input-output parts of a peripheral device with use of separate interfaces. The numerical controller controls axes by transmitting motion commands to amplifiers of the motor driving parts and thus operating motors at a predetermined cycle in accordance with given machining programs. The numerical controller also carries out output control for the peripheral device in accordance with given programs.
Usually, however, there are differences in data transfer cycle, data transfer rate, and/or the like between the interface connected to the amplifiers and the interface connected to the peripheral device and thus a time lag associated with data transfer is caused. The time lag associated with the data transfer may be a factor that deteriorates control accuracy for the peripheral device.
For laser beam machining systems, for instance, control over output conditions such as emission, halting, peak power, frequency, and the like of a laser beam is demanded as the output control over the peripheral device. Under a condition of a machining speed in a conventional laser beam machining system, deterioration in the accuracy due to the time lag associated with the data transfer is not so highly problematic. With increase in laser machining speed in recent years, however, problems due to the deterioration in the accuracy have become obvious and synchronization between the control over servomotors and the control over the peripheral device has been demanded.
Japanese Patent Application Laid-Open No. 2006-247745 discloses a technique that eliminates the deterioration in the accuracy in the control over the peripheral device due to the time lag associated with the data transfer by connection of the motor driving parts and the peripheral device to a numerical controller with use of common communication lines and standardization of their respective interfaces.
Communication with a communication cycle on the order of 1 millisecond is used for the control over the peripheral device in such a machine as machine tool. On the other hand, the servomotors, for which high accuracy and response at accordingly higher speed are demanded, are controlled by communication with a cycle on the order of 125 microseconds to 1 millisecond. For the laser beam machining described above, however, demands for the control at a further higher speed and with further higher accuracy have been developing.
Japanese Patent Application Laid-Open No. 2006-247745 mentioned above discloses the technique by which the interfaces and the communication lines are standardized with regard to the communication used for output control over a peripheral device such as a laser oscillator and the communication used for control over servomotors. Thus, the control over output of the laser oscillator is made faster by being synchronized with the servomotors, thereby the problems are solved. It is not mentioned in the patent document, however, that information from sensors connected to the peripheral device and the like are reflected, as an input, in the control.
As means for reflecting the sensor information acquired from the peripheral device and the like, as an input, in the control, it is conceivable that the sensor information is transmitted from the peripheral device through the communication lines to a side of the numerical controller. On condition that there are a large number of types of the sensor information acquired from the peripheral device, however, it is thought that increase in ratio of sensor information in the communication may cause oppression of a communication band. It is thought as well that increase in a load on a processor on the side of the numerical controller for processing of the sensor information may interfere with the usual control over the motors. Furthermore, it is difficult to control the output with a time resolution shorter than the communication cycle of the communication lines because the sensor information acquired from the peripheral device is transferred via the communication lines to the processor that processes control inside the numerical controller, processed therein, and thereafter transferred to the output part of the peripheral device.